1. Field of the Invention
The present invention relates to a thin film transistor substrate and a liquid crystal display having the same, and more particularly, to a thin film transistor substrate with dummy patterns formed outside the outermost data lines to compensate for a charging rate and a liquid crystal display having the thin film transistor substrate.
2. Description of the Related Art
A liquid crystal display (“LCD”) includes a thin film transistor (“TFT”) substrate with pixel electrodes formed thereon, a color filter substrate with a common electrode formed thereon, and a liquid crystal layer interposed between the TFT and color filter substrates. In the LCD, an electric field is produced in the liquid crystal display by applying voltage to the pixel and common electrodes. The applied electric field controls the orientation of liquid crystal molecules in the liquid crystal layer and the orientation of the liquid crystal molecules in the liquid crystal layer thereby controls the polarization of incident light. Typically, LCD displays include a plurality of pixels, each pixel capable of independently controlling the amount of incident light passing therethrough.
Gate and data lines for transmitting scanning and image signals, respectively, extend substantially perpendicular to each other, on the TFT substrate. Each pixel of the LCD is connected to at least one data line and at least one gate line and each pixel occupies a pixel region. A TFT and a pixel electrode are formed in each pixel region. The TFT is connected to the gate and data lines, and the pixel electrode is connected to the TFT. Here, the TFT is a switching element allowing an image signal transmitted through the data line to be transmitted to the pixel electrode or cut off depending on the state of a scanning signal transmitted through the gate line.
Moving images may be shown by rapidly displaying a series of slightly changing images. Each image in the series is called a frame.
As the resolution and sized of LCDs have increased the requirement for lightweight, thin and small-sized components for the LCD has also increased. In order to implement a high resolution display, the number of pixels, and therefore also the number of data and gate lines, is essentially increased. Particularly, if the number of data lines is increased, the number of data driving integrated circuits (“ICs”) for applying image signals to the data lines is also increased. Therefore, the size of an LCD enlarges.
An LCD with a reduced number of data driving ICs has been suggested to reduce the size of the LCD while maintaining a high resolution. In this case, the number of gate driving ICs should be increased instead; therefore a Gate IC Integration (“GII”) method of integrating gate driving ICs in a panel is generally applied at the same time. Further, in order to effectively arrange the gate lines in increasing numbers, pixels are arranged in an abscissa (or x-axis) direction. Charging time for each frame in such an LCD display is insufficient for fully charging a data voltage from the data line to a corresponding pixel electrode. Therefore, a line reversal method, wherein each data line is driven at a voltage substantially opposite a common voltage, is used to compensate for the slower charging time. Further, in order to implement a pixel reversal while maintaining a line reversal method, TFTs connected to each data line may be arranged alternately left to right along the respective data line, thereby forming a zigzag pattern.
After TFTs are arranged alternately right and left in a zigzag pattern with respect to a data line, another data line may be added at each outermost side thereof. As such, each outermost data line is connected to half as many pixels as other respective data lines. For example, the leftmost data line is connected to the pixels only at the right side thereof, and the rightmost data line is connected to the pixels only at the left side thereof. Thus, the outermost data line differs from the other data lines in a capacitance between gate and drain electrodes. Accordingly, since the capacitance of the outermost data line is smaller than that of the other data lines, the charging rate of the pixels connected to the outermost data line is higher than that of the pixels connected to the other data lines.
Further, since there are only approximately half the pixels connected to each outermost data line as those connected to each of the other data lines, liquid crystal capacitors Clc and storage capacitors Cst of the pixels connected to the outermost data line are approximately half as large as those connected to the other respective data lines. Thus, the charging rate of the pixels connected to the outermost data lines is higher than that of the pixels connected to the other data line.
Since the charging rate of pixels connected to such an outermost data line is higher than that of pixels connected to other data lines, a display failure such as wrinkling stripes appears along the left and right sides of a panel. For example, a pixel with a display failure appears darker than adjacent pixels in a case of a twisted nematic (“TN”) mode LCD, and appears brighter than adjacent pixels in a case of a patterned vertical alignment (“PVA”) mode LCD.